[fox46]

This reminds me of an experience I once had with some lexan sheet. Lexan is normally a very resilient material very resistant to a brittle fracture. On one of my projects I had used lexan panels as body parts on a vehicle. A friend of mine who was helping out decided to clean them using aerosol brake cleaner. After wiping them down with the brake cleaner and a rag, approximately one hour later the entire panel shattered into tiny pieces. We deduced that the chemical agents in the brake cleaner had been absorbed into the plastic causing it to become incredibly brittle. It is possible that a similar process may have affected these two tanks.